U.S. Pat. No. 4,669,318 (Ångström) concerns an apparatus for dynamometer testing of motor vehicles, wherein load absorbing means in the form of a hydrostatic pump assembly has an input shaft for engagement with a drive shaft of a vehicle to be tested. Sensor means are arranged so as to allow measuring the torque from the vehicle drive shaft. Typically, in a vehicle having two wheel drive, each drive shaft is connected to an individual apparatus of this kind, whereby a total effective torque from the vehicle can be accurately measured.
The apparatus according to the background art is reliable and accurately measures torque in a steady load situation.
Recently there have been demands for testing appliances that can more truly mimic a true vehicle driving situation taking into account the dynamic conditions prevailing during real life driving of the vehicle on a road.
Roller type dynamometers equipped with large rollers that support vehicle wheels are previously known, but this kind of appliances does, however, not allow full measurement freedom.
As representatives of the background art can also be mentioned U.S. Pat. No. 6,754,615 which discloses a method of simulating the performance of a vehicle on a roadway with the help of torque controlled electric load machines and U.S. Pat. No. 4,939,985 which discloses a test bench for testing the drive train of a vehicle using electric load machines. These two latter constructions are overly complex, require extensive electrical installation, require fixed installation sites and are not particularly flexible.